Income Taxes (Other Taxes) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes [Abstract]
Gross Receipts/Delivery	$ 145	$ 145	$ 142
Property	71	70	68
County Fuel and Energy	170	154	94
Environmental, Use and Other	65	65	64
Total	$ 451	$ 434	$ 368

A tax based on the assessed value of real estate by the local government. The tax is usually based on the value of property (including the land).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 43

-Chapter 10

-Section A

-Paragraph 2, 17

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 720

-SubTopic 30

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6419918&loc=d3e35301-107843

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration